This invention relates to a metallic hollow profile member with at least one outer flange or projection formed as an extension of a side edge and with a plastic or synthetic resin sheath extruded onto the metallic hollow profile member. The frame elements formed by such plastic encased hollow metal profile members are especially useful for making door and window frames.
In conventional profile members, the bearing surfaces and fittings formed at the relatively soft plastic sheath are fashioned to be self-supporting and thus are unsuitable for greater stresses. Furthermore, plastic-encased metallic hollow profile members have been contemplated wherein the hollow metallic profile member is constructed with projecting stops or contact surfaces, wherein, however, the plastic casing is seated relatively loosely on the metallic core and is detached in the zone of the corners. This relatively loose seating of the synthetic resin sheath on the metallic core also has the disadvantage that often a subsequent shrinking of the plastic casing can occur. The stresses resulting from the shrinking can have such an effect on the weld seams at the junction points of such profile members (for example when used as window and door frames), that these seams sometimes rupture.
The present invention contemplates overcoming the above-discussed problems by providing a profile member having satisfactory strength properties and by affording a flawless seating of the plastic casing on the profile member, so that they can be satisfactorily processed into final products.
According to the present invention, the plastic sheath is fixed in the outside corner formed between the outer flange and the joined adjacent side wall of the hollow metallic profile member. In preferred embodiments of this invention, the plastic sheath is fixed at the outside corner by forming the hollow metallic profile member, in the zone of the corner, with at least one projecting cam, forming an undercut corner groove, and by fashioning the plastic sheath correspondingly at the corner with a cam strip engaging the corner groove. By means of the fixation of the plastic sheath in the set-back corners of the reinforcing metal core, according to the present invention, a flawless seating of the loose plastic sheath is ensured. In this way, stable and friction-fitting, plastic-encased hollow profile members can be produced by extruding the synthetic resin sheath onto the hollow profile member. The present invention also contemplates providing preferred embodiments where the hollow profile member is furthermore roughened by fluting, pitting, sand-blasting, or corresponding surface treatment in order to increase the tight fit between the metallic hollow profile member and the plastic sheath.
In preferred embodiments of the invention, the interlocking elements serving for the fixation of the plastic sheath in the corner formed by the outer flange and the metallic hollow profile member are fashioned to be symmetrical.
In certain preferred embodiments, the plastic sheath, as seen in cross-section, contacts the metallic hollow profile member flush at all points. In other preferred embodiments, the connection is such in the zone of the corner that the plastic sheath, in the zone of the corner, contacts the metallic hollow profile member only partially while being firmly held in position.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.